Integrated circuits (ICs), the key components in thousands of electronic systems, generally include interconnected networks of electrical components fabricated on a common foundation, or substrate. Conductive interconnects are used to electrically connect semiconductor devices, such as capacitors or transistors, or to define a specific IC, such as a computer memory or microprocessor. The quality of the conductive interconnects greatly affects overall manufacturability, performance, and lifetime of the IC. Thus, the material used to form the conductive interconnects is increasingly determining the limits in performance, density, and reliability of integrated circuits.
For example, electrical conductivity of interconnects is extremely significant to the operational speed of the integrated circuit (IC). Aluminum (Al) and alloys thereof have been widely used as interconnect materials in semiconductor devices based on their low resistivity and ready adhesion to interlayer dielectric materials, such as silicon dioxide (SiO2). Unfortunately, aluminum is susceptible to corrosion and offers poor resistance to electromigration, which increases the potential for open circuits from voids or short circuits.
In an attempt to improve the performance, reliability, and density of the conductive interconnects, alternative metals to aluminum and aluminum alloys are being explored. To improve conductivity in the wiring, it has been proposed that copper (Cu) and alloys thereof be used to form conductive interconnects. However, copper rapidly diffuses through many conventional dielectric materials to form undesired copper oxide compounds. In addition, copper does not adhere well to conventional dielectric materials or to itself.
Silver (Ag) has also been proposed as a substitute for aluminum-containing conductive interconnects and is becoming increasingly significant in use as an electrochemically active material in electrodes of programmable memory cells, such as those of conductive bridge random access memory (conductive bridge RAM) cells. Silver has an extremely low resistivity, but is difficult to deposit in narrow gaps (e.g., gaps having a dimension of 20 nm or less) due to limitations on currently available deposition techniques. While silver may be deposited by sputtering (physical) deposition techniques, these techniques are not suitable for filling narrow gaps with silver. Furthermore, interconnects have been difficult to form from silver due to adhesion issues and agglomeration at increased temperatures. Since silver is resistant to dry etch processes, conventional techniques for forming semiconductor conductive elements (e.g., interconnects and electrodes) are impractical for making such conductive elements from silver.